It is the purpose of the present continuation in part application to describe a simplified and improved embodiment over that disclosed in my co-pending application, Ser. No. 738,523, filed Nov. 3, 1976 now abandoned. This invention permits the detection of the presence of a child in the protected swimming pool in time to prevent drowning. The apparatus of the present invention can detect the presence of a child in the pool whether he falls in or enters the water gently. The present apparatus can be installed at any location on the pool or even at a remote location and connected to pool water by pipe or syphon without range or sensitivity problems. Unlike the prior art, the apparatus of the present invention does not respond to waves, ambient sound, water pressure or transitory water disturbance, nor does the present invention utilize floats or moving mechanical parts which have troubled the prior art.